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Yesterday, Beijing was hit by heavy snow. Overnight, the red walls and green tiles were covered with white snow, which reminded me of a line by the poet Yin Lichuan: "When it snows, Beijing becomes Beiping."

For office workers, the most healing thing at this moment is a cup of warm and fragrant coffee. Instant coffee has become the only choice for many people because of its convenience and low cost.

However, while enjoying instant coffee, the public also has various questions about it.

How is instant coffee made? Does the production process damage the original aroma of coffee beans? What is acrylamide in coffee?

In the next three minutes, let us follow the footsteps of Yun Wuxin, a master of biology from Tsinghua University, a doctor of biological and food engineering from Purdue University, scientific consultant for the documentary "A Bite of China 2", and a popular science writer, to find the answer in his new work "He Who Knows Food Is a Hero: Yun Wuxin's Food Science".

1

Coffee is one of the three major beverages in the world. It has a long history of drinking abroad and is now gradually entering the daily life of Chinese people. However, making coffee is still a troublesome thing for most Chinese people, so instant coffee is particularly attractive to Chinese people.

The earliest production of instant coffee can be traced back to the late 18th century in Britain, while in the United States, the first instant coffee test products appeared in the mid-19th century. In 1890, a New Zealander first obtained a patent for instant coffee. In 1901, a Japanese perfected the technology for making instant coffee, but it was not until around 1910 that the technology for making instant coffee was industrialized by Americans.

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At that time, instant coffee only solved the problem of "instant dissolution", and people did not like the taste. The real spring of instant coffee was in 1938, when Nestlé entered this field and improved the production technology of instant coffee, especially adding an equal amount of soluble carbohydrates before drying to improve the taste. Nestlé's instant coffee immediately became popular, especially among soldiers in the army - during World War II, the instant coffee produced by Nestlé was once exclusively supplied to the army.

2

The idea behind making instant coffee is not complicated. The coffee beans are roasted, which is the same as the production of regular coffee. The natural ingredients in them undergo complex chemical reactions to produce various aromatic substances. Then, the coffee beans are ground into powder and extracted with high-temperature water. This high temperature is achieved under high pressure, and the water temperature is far more than 100°C, so the extraction efficiency is very high. The extract contains soluble coffee ingredients, which are concentrated and dried to obtain instant coffee powder. When the instant coffee powder is added to water, it can be easily dissolved. The "instant" in instant coffee is actually translated into "instantly soluble" in English. The translation into "instant" is just for the sake of being more fluent.

Drying is another critical step in producing instant coffee.

Currently, there are two ways to dry coffee extract in the industry. One way is to freeze the concentrated extract to dozens of degrees below zero, then evacuate it to make the ice directly turn into steam to remove the water. This method is called " freeze drying ", which can keep the coffee unchanged and help preserve the flavor of the coffee, but it is relatively expensive.

Another method is called " spray drying ". The concentrated extract is sprayed downward from a high tower top into mist, and high-temperature air is blown upward from the bottom of the tower. The mist droplets containing coffee are heated by the hot air during the falling process, and the water evaporates and falls to the bottom of the tower and becomes dry powder. This method is efficient and low in cost, but because it requires high-temperature heating, some of the coffee's aroma substances will change, and those volatile aroma substances will also be lost due to evaporation.

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In the production process of instant coffee, the loss of aroma substances does not only occur in the drying stage. In fact, in every step from grinding coffee beans to extraction, concentration, and drying, coffee will lose some aroma substances. If no remediation is done, the resulting product can only be "instant powder" without "coffee flavor". Therefore, instant coffee producers will add aroma substances to remedy the situation. As for what to add and how to add it, it has become the specialty of different manufacturers - some only add it in the last step, some add it in some of the previous steps or even every step; some "recover" the lost aroma substances and add them, and some directly add flavors and spices. Generally speaking, no matter how it is added, instant coffee is still difficult to restore the flavor of freshly brewed coffee.

Because the flavor substances of instant coffee always go through a cycle of "loss-addition", the quality of the initial coffee beans is not so important, which makes it possible to make instant coffee powder from less high-quality coffee beans. In addition, after being made into instant coffee, the finished product is smaller in volume than coffee beans, and the packaging, storage, and transportation costs required are also lower. In short, instant coffee not only brings convenience to consumers, but also increases the supply capacity of coffee raw material suppliers.

Compared to freshly brewed coffee, instant coffee sacrifices some flavor in exchange for convenience, which is unacceptable to people who put "taste first", but is attractive to those who think "convenience is the most important."

3

Many people are concerned about acrylamide in instant coffee. High doses of acrylamide are neurotoxic, and various starchy foods that have been baked or fried at high temperatures often contain a certain amount of acrylamide. Coffee beans also produce some acrylamide after being roasted.

The acrylamide content in instant coffee is close to that in freshly brewed coffee, and the acrylamide content in instant coffee is at the same order of magnitude as that in potato chips, biscuits, and nuts. If you consider that it takes several times or even ten times more water to make coffee powder into a coffee drink, the amount of acrylamide you ingest from drinking instant coffee is not that much.

The instant coffee that many people drink is actually not just coffee, but a coffee drink. Such coffee drinks are usually called "two-in-one" or "three-in-one" instant coffee.

"Two-in-one" is usually instant coffee powder plus coffee creamer, while "three-in-one" is added with sugar. Coffee creamer is also called non-dairy creamer, which is mainly syrup plus emulsified oil. Some non-dairy creamers use hydrogenated vegetable oils, which may contain trans fats, which is the main reason why non-dairy creamers are accused of being harmful. However, this is the same as adding sugar and creamer to freshly brewed coffee - if you don't want these "unhealthy additives", buy a single instant coffee powder and you can get "black coffee" after brewing .

The above content is excerpted from:

Book title: "Those who know food are heroes: Yun Wuxin's popular science on food"

Author: Yun Wuxin

Publisher: Chongqing Publishing House

Book number: 978-7-229-14109-7

Publication date: November 2019

List price: 48.00

Category: Health Science